There is a strong evidence (see page 36 "Divalent Carbon" by Jack Hine, The Ronald Press Comp., New York, 1964) that upon treatment with an aqueous solution of a strong base a haloform undergoes the following reactions to give the reactive intermediate dihalocarbene (dihalomethylene): EQU CHHal.sub.3 + OH.sup.- .revreaction. CHal.sub.3 .sup.- + H.sub.2 O EQU chal.sub.3 .sup.- .fwdarw. CHal.sub.2 + Cl.sup.-
In the above equations Hal represents a halogen atom. The dihalomethylene readily reacts with water to form carbon monoxide and hydrogen halide.
Makosza et al (see Tetrahedron Letters 53 (1969) 4659 - 62) have contacted aqueous sodium hydroxide with chloroform containing an olefin in the presence of a catalytic amount of triethylbenzylammonium chloride. They found that the corresponding gem-dichlorocyclopropane derivative was formed: ##STR1##